The flux growth of crystals of YBa2Cu3O7-?

The flux growth of crystals of YBa2Cu3O7-? is reported. The composition (3CuO + BaO) was successfully used as flux and the melt was slowly cooled from 1280 °C. The crystals were characterised by X-ray powder patterns, by single crystal X-ray study and by EPMA. Because a reaction with dissolved platinum resulted in crystals of Y2Ba3Cu2PtO10, a high soak temperature followed by a very slow cooling programme has to be avoided. Alternative crucible materials were investigated but BN, sintered Al2O3, stabilised ZrO2, and SnO2 single crystals all reacted with the melt in less than three days. Infrared reflectance was used to examine the electronic state of the crystals before and after annealing. After annealing the single crystal was superconducting.